Fix tests

ftplugin/dockerfile.vim

@@ -0,0 +1,20 @@
+if !exists('g:polyglot_disabled') || index(g:polyglot_disabled, 'dockerfile') == -1
+
+" Vim filetype plugin
+" Language:	Dockerfile
+" Maintainer:   Honza Pokorny <http://honza.ca>
+" Last Change:	2014 Aug 29
+
+" Only do this when not done yet for this buffer
+if exists("b:did_ftplugin")
+  finish
+endif
+
+" Don't load another plugin for this buffer
+let b:did_ftplugin = 1
+
+let b:undo_ftplugin = "setl commentstring<"
+
+setlocal commentstring=#\ %s
+
+endif